This invention relates to an apparatus for producing operating fluid of high pressure from operating fluid of low pressure.
Conventionally, hydraulically-operated devices or apparatus used in the various fields of industry (e.g. construction, transportation, agriculture) are mainly operated with an operating fluid of low pressure (70.about.210 kg/cm.sup.2). However, among such hydraulically-operated devices, there exist several devices which requires a fluid circuit of high pressure (700.about.1000 kg/cm.sup.2) such as hydraulic jacks, shearing machines, or press means and also devices which show better operating performance with high pressure fluid than low pressure fluid.
Conventionally, for operating such devices which necessitate or prefer fluid at high pressure, a hydraulic motor is primarily driven by a fluid of either intermediate or low pressure and subsequently the output of the motor is imparted to a plunger pump for producing the high pressure fluid. In another conventional method or device, two pressure increase mechanisms which have different pressure areas are alternately driven by the actuation of valve means such as solenoid valves, wherein two pressure increase mechanisms are alternately reciprocated so as to produce a high pressure fluid on the high pressure side of the device. However, since the above-mentioned conventional methods or devices require additional or separate devices besides the pressure increase mechanisms, the entire construction of the devices become complicated and cumbersome resulting in high production cost.
It is an object of the present invention to provide a pressure converting apparatus which can automatically and accurately convert fluid of low pressure to fluid of high pressure.
It is another object of the present invention to provide a pressure converting apparatus which can be produced at a considerably low cost.
The pressure converting apparatus of this invention, in summary, comprises:
(a) low pressure and high pressure cylinders connected coaxially, such respective cylinders having low pressure and high pressure cylinder chambers of different effective bore areas, PA1 (b) a coaxial piston rod slidably disposed in the coaxial low pressure and high pressure cylinder chambers, the coaxial piston rod being provided with low pressure and high pressure pistons at opposed longitudinal ends thereof, the low pressure and high pressure pistons dividing the respective cylinder chambers into a front piston chamber and a rear piston chamber, PA1 (c) a rear cover block attached to the rear of the low pressure cylinder, the rear cover block incorporating a low pressure liquid inlet and directional control and pilot valves, the directional control valve and pilot valve cooperating so as to alternately supply low pressure fluid into the front and rear piston chambers of the low pressure cylinder, PA1 (d) an automatic pilot valve operating mechanism incorporated in the rear cover block, said mechanism being operably interconnected with the movement of said piston rod so as to operate said pilot valve, corresponding to the movement of said piston rod, PA1 (e) a secondary fluid supply line bypassing a portion of low pressure fluid discharged from the pilot valve to the chambers of high pressure cylinder, and PA1 (f) a suction valve and an exhaust valve disposed in the secondary fluid supply line, such suction and exhaust valves being operably interconnected with the movement of the high pressure piston in the high pressure cylinder chambers enabling the high pressure cylinder to pump out high pressure fluid through a high pressure fluid outlet formed in the high pressure cylinder twice per one reciprocation of the coaxial piston rod.